Photosensitive composition comprising polyurethane prepolymer

ABSTRACT

A PHOTOSENSTIVE COMPOSITION COMPRISING A POLYURETHANE PREPOLYMER AND A PHOTOSENSITIZER, THE PREPOLYMER BEING PREPARED BY THE REACTION OF A HYDROXYL COMPONENT HAVING AT LEAST 5 ETHER LINKAGES AND AN ETHYLENICALLY UNSATURATED DOUBLE BOND POSITIONED AT THE TERMINALS WITH A POLYISOCYANATE COMPONENT.

United States Patent US. Cl. 96-115 R 8 Claims ABSTRACT OF THEDISCLOSURE A photosensitive composition comprising a polyurethaneprepolymer and a photosensitizer, the prepolymer being prepared by thereaction of a hydroxyl component having at least ether linkages and anethylenically unsaturated double bond positioned at the terminals with apolyisocyanate component.

This invention relates to a photosensitive composition suitable as amaterial for the production of better press printing plates andflexographic printing plates, which comprises a polyurethane prepolymer,a photosensitizer, and if desired, an ethylenically unsaturated monomer,the prepolymer being obtained by the reaction of a hydroxyl componentcontaining at least 5 ether linkages and an ethylenically unsaturateddouble bond positioned at the terminals with a polyisocyanate component.

Flexographic printing is a method suitable for printing packagingmaterials such as cellophane, glassine paper, kraft paper, corrugatedcardboard, polyethylene films, polypropylene films, polyvinyl chloridefilms, polyester films, or aluminum foils. With an increasing demand forpackaging materials, flexographic printing has been needed more thanever.

In flexographic printing, rubber plates have been previously used. Therubber plates have been produced by a series of complicated processsteps including the production of an original metal plate through thesteps of graining the surface of a metal plate, coating a photosensitivesolution on the surface of the metal plate, drying the coating, exposingand developing, strengthening the photo cured film, and etching theplate, applying a matrix material to the metal plate and pressing it toform a matrix, and thereafter, fabricating and curing the rubber usingthis matrix.

As an improvement of this process, British Pat. 1,131,-

617 discloses a method of producing flexographic printing plates ofsynthetic resin from a photosensitive composition, by a simpleoperation, which comprises irradiating actinic rays onto a layer of aphotosensitive composition containing an unsaturated polyester resin, aphotosensitizer and a cross linking agent through a negative or positivefilm to photopolymerize the exposed part, removing the unexposed part bywashing with water or an aqueous solution containing an acid, alkali ororganic solvent, and developing the exposed part.

In the production of flexographic printing plates of synthetic resins,the photosensitive compositions to be used must meet the followingrequirements.

(1) The exposed portion of the photosensitive composition should bephotopolymerized by the application ICE of actinic light to a rubberyelastomer insoluble in organic solvents.

2) The unexposed part of the photosensitive composition should bereadily soluble in water or an aqueous solution of an acid, alkali, ororganic solvent, and the exposed portion should be easily developed.

(3) Re-exposure can be effected with simple operation after thedevelopment in order to increase the strength of the resultingfiexographic plates.

(4) The flexographic printing plates formed by the photopolymerizationof the photosensitive composition should have good abrasion resistance.

(5) The resulting flexographic printing plates should not be swollen ordissolved by printing ink.

(6) Printing ink should adhere well to the flexographic printing plates,and the ink transfer from the flexographic plates to the material to beprinted. should be excellent.

The photosensitive composition disclosed in British patent specification1,131,617 has the tendency that its photopolymerization is retarded .bythe presence of oxygen in air. The re-exposing of the developedflexographic plate should be performed in nitrogen gas. This is acomplicated procedure. Furthermore, since the photosensitive compositioncontains a great amount of ester linkage due to the unsaturatedpolyester resin, the resulting flexographic plate has poor resistance toalkalies, and is liable to be attacked by an alkaline printing ink.

Accordingly, it is an object of the present invention to provide aphotosensitive composition having all the properties described above.

It has been found that a photosensitive composition comprising apolyurethane prepolymer, a photosensitizer, and if desired, andethylenically unsaturated monomer, the prepolymer being obtained by thereaction of a hydroxyl component containing at least 5 ether linkagesand an ethylenically unsaturated double bond positioned at the terminalswith a polyisocyanate component meets the.v above-mentioned object ofthe invention. As the hydroxyl component mentioned above, the use of ahydroxyl compound having at least 5 other linkages and an ethylenicallyunsaturated double bond at the terminals (hydroxyl Compound A for short)is most convenient. It is also possible to use a combination of :ahydroxyl compound having at least 5 ether linkages (hydroxyl Compound B.for short) and a hydroxyl compound having an ethylenically unsaturateddouble bond positioned at the terminals (hydroxyl Compound C for short),or a combination of Compound A and hydroxyl Compound B and/or hydroxylCompound C.

When actinicrays are irradiated onto a layer of the photosensitivecomposition of the present invention, through a negative or positivefilm, the unexposed portion can be removed by dissolving it in water oran aqueous solution of an acid, alkali, or organic solvent, but theexposed portion undergoes photopolymerization and becomes a rubbery.elastomer which is insoluble in water, an aqueous solution of an acid,alkali, organic solvent, and also in organic solvents. Thephotosensitive composition of the invention can be ,photopolymerized inthe presence of oxygen. The flexographic plates produced from thisphotosensitive composition have superior resistance to alkalies.Therefore, the photosensitive composition of the present invention hasremoved all of the defects of the photosensitive composition disclosedin the British patent specification 1,13l,617, and can fully exhibit theproperties (1) to (6) described above.

As previously stated, the photosensitive composition of the invention issoluble in water or an aqueous solution containing an acid, alkali ororganic solvent before being photopolymerized, but whenphotopolymerized, it becomes a rubbery elastomer which is no longersoluble in water or the aforementioned aqueous solution or in organicsolvents. This is due to the presence of or more ether linkages whichare due to the hydroxyl compound A or hydroxyl compound B in thehydroxyl component.

Examples ofthehydroxyl-Compound A are:

polypropylene glycol monomethacrylates of the formula CH2=(3CO O(CHzCH0) H.

CH3 (5H2 (n is an integer of 6 to200) polyethylene glycolmonomethacrylate's of the formula C cH2=C-COO(cHzCHgO) H CHs ' (n is aninteger of 6 to 200) polypropylene glycol monoacrylates of the formulaCHn=CHC O O (CH2(EHO)H CH3 n (n is an integer of 6 to 200) polyethyleneglycol monoacrylates of the formula (n is an integer of 6 to 200) orhydroxyl compounds of the general formula CHgCHPJY-CHzO (CHzOHO )H m I(l, m and n are each zero or a positive integer, and satisfy therelation 'of l+m+n is an integer of 5 to 200).

These hydroxyl compounds may be used either alone or in combination. I

Examples of the hydroxyl Compound B include:

polyethylene glycols of the formula (n is an integer of 6 to 200)polypropylene glycols of the formula H0 (CHnCHaO )mH mowmomonn I V: Mthe relation of l+nil+n being an integer of to -polyoxypropylatedglycerolofthefor-mula (1, m and II are each zero or a positive integer,and satisfy i I :7 V: 200);

CHZO CHZCHO H (l, m and n are the same as defined above);polyoxyethylated trimethylolpropanes of the formula omowmomonntemom-o-omb om'ommmn cmowmcmmln (l, m, and n are the same as definedabove); poly'oxypropyla-ted trimethylolpropanes of the formula l CH; 1CHaCHr- CHaO CHzCHO H CHiCHO H (l, m, and n are the same as definedabove); hydroxyl compounds of the formula v HO omomo)t(CH,oHO)m(CHiCH1O)nH (l, m, and n are each a positive integer of atleast 1 and OHIO satisfy the relation of l+n z+n being an integer of 5to polyoxetane compounds such aspoly[3,3-bis(chloromethyDoXyacycIobutane] of the formula I CHaGlHO(CH1&CH:O H

moi (n is an integer of 6 to 200).

These hydroxyl Compounds B may be used either alone or in combination.

That the prepolymer of the present invention can be photopolymerizedeven in the presence of oxygen in air is due to the presence of anethylenicallyunsaturated double bond at the terminals which is due tothe hydroxyl Compound A or hydroxyl Compound C inthe hydroxyl componentof the prepolymer.

Examples of the hydroxyl Compound C include 2-hydroxyethyl' acrylate,2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, Z-hydroxypropylmethacrylate,

N-hydroxymethyl acrylamide, N-hydroxymethyl meth-' acrylamide,diethylene' glycol monoacrylate, diethylene' glycol monomethacrylate,hydroxystyrene, glycerol dimethacrylate, an equimolar reaction productof glycidyl methacrylate and acrylic acid, trimethylol propane d1-methacrylate, trimethylpropane monomethacrylate, pentaerythritoltrimethacrylate, pentaerythritol dimethacrylate, pentaerythritolmonomethacrylate, allyl alcohol, 2-brom'o allyl alcohol, or2-'chloroallyl alcohol. These hydroxyl be used either alone or incombinaflexophaphic plate, another hydroxyl compound (to be referred toas the hydroxyl Compound (D) different from the hydroxyl Compounds A, Band C described above may be used as part of the hydroxyl component ofthe prepolymer of the invention.

Examples of the hydroxyl Compound D that can be used in the inventioninclude octyl alcohol, decyl alcohol, tridecyl alcohol, stearyl alcohol,ethylene glycol monoethyl ether, ethylene glycol, propylene glycol,diethylene glycol, dipropylene glycol, triethylene glycol, 1,3-butyleneglycol, 1,4-butylene glycol, neopentyl glycol, trimethylolpropanemonoacetate, glycerol, trirnethylolpropane, trimethylolethane,pentaerythritol, and sorbitol. These hydroxyl Compounds D may be usedeither alone or in combination.

In the present invention, the ethylenically unsaturated double bondcontained in the prepolymer is restricted to that positioned at theterminals. This is because of the necessity of enabling thephotosensitive composition containing the prepolymer to bephotopolymerized even in air. The especially preferred ethylenicallyunsaturated double bonds are those based on an acryloyl group,methacryloyl group or ethacryloyl group expressed by the general formulawherein R is a hydrogen atom or a methyl or ethyl group.

The polyisocyanate component to be reacted with the hydroxyl componentto form the prepolymer is a compound having at least 2 isocyanate groupsin the molecule. Examples of such polyisocyanate compounds are 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, xylylene diisocyanate,3,3 dimethyldiphenylmethane-4,4-diisocyanate, 2,4-tolylenediisocyanatedimer, 1,5-naphthylene diisocyanate, a triphenyl urethane reactionproduct between hexanetriol and 2,4-t0lylene diisocyanate, a triphenylurethane reaction product between trirnethylolpropane and 2,4-tolylenediisocyanate, metaphenylene diisocyanate, triphenylmethane 4,4',4"triisocyanate, hexamethylene diisocyanate, a biuret compound ofhexamethylene diisocyanate compound. These polyisocyanate compounds maybe used either alone or in combination. If desired, a monoisocyanatecompound having one isocyanate in the molecule such as phenylisocyanate, n-butyl isocyanate, n-octyl isocyanate, stearyl isocyanateor methoxyethyl isocyanate may be used in the preparation of theprepolymer together with the polyisocyanate compounds described.

The ether linkage possessed by the hydroxyl Compound A and the hydroxylCompound B (both of these will be generically termed polyether-typehydroxyl compound hereinafter) serves to increase the solubility of thephotosensitive composition in water or an aqueous solution, and also toimpart rubbery elasticity to the flexographic printing plate obtained.In order to achieve the aforementioned effects fully by using thehydroxyl Compound C and the hydroxyl Compound D together with thepolyether-type hydroxyl compound, it is desirable to use thepolyether-type hydroxyl compound in an amount of at least M+0.8E o eperson based on the total amount of the hydroxyl compounds. In the aboveequation, M is an average molecular weight of the hydroxyl Compounds Cand D. If there are n n n, moles of the hydroxyl compounds having amolecular weight of m m m,, then and E is an average molecular weight ofthe polyethermoles of polyether-type hydroxyl compounds having amolecular weight of e e 2 then -lua E Em For example, when polyethyleneglycol having an average molecular weight of 1,540 (hydroxyl CompoundB), polyethylene glycol having an average molecular weight of 200(hydroxyl Compound D), and Z-hydroxyethyl methacrylate (hydroxylCompound C) are used at a molar ratio of 1:9,

M 137 M+0.8E 137+0.8 1540 Therefore, it is desirable to use at least10.0 mole percent of polyethylene glycol having an average molecularWeight of 1540 based on the total amount of the hydroxyl component ofthe prepolymer. As another example, when triethylene glycol (hydroxylCompound D) and polyethylene glycol monomethacrylate having an averagemolecular weight of 468 (hydroxyl Compound A) are used as the hydroxylcomponent,

M 150 M+0.8E 150+0.8 X468 It is therefore desirable to use polyethyleneglycol monomethacrylate having an average molecular weight of 468 in anamount of at least 28.6 mole percent based on the total weight of thehydroxyl component. As still another example, when 2-hydroxyethylacrylate (hydroxyl Compound C) and polyethylene glycol monomethacrylatehaving an average molecular weight of 1000 (hydroxyl Compound A) areused as the hydroxyl component,

M 116 M+0.8EX100 116+0.8 1000X100 127 tion with the amount of theethylenically unsaturated.

double bonds at the terminals which the hydroxyl Com pound A and/or thehydroxyl Compound C has. When the total amount of the hydroxyl componentand the polyisocyanate component used in the preparation of theprepolymer is W grams and there are n n n moles of the hydroxyl CompoundA and/ or the hydroxyl Compound C each having N N N ethylenicallyunsaturated double bonds at their terminals, a value is expressed by theequation If is in excess of 9,000, it is very difficult to cure thephotosensitive composition within a short period of time, and theresistance to chemicals of the resulting flexographic printing platebecomes abruptly poor. When a far superior printing durability isrequired to the fiexographic plate, it is desirable to adjust the valueof to below 7,000.

The ratio of the hydroxyl component to the polyisocyanate componentexerts serious effects on the solubility of the photosensitivecomposition in water or an aqueous solution containing an acid, alkalior organic solvent, its viscosity, its shelf life, and the physicalproperties of the flexographic printing plate. Generally, it isdesirable to react both of these components so that the followingrelation exists wherein H is the number of hydroxyl groups contained inthe hydroxyl component, and I is the number of isocyanate groupscontained in the polyisocyanatecomponent.

When unreacted active isocyanate groups remain in the resultingprepolymer, the concentration of the isocyanate groups should beadjusted to below 0.5% by weight based on the total weight of thephotosensitive composition.

In order to effect the reaction of producing the prepolymer smoothly, anorganic solvent or ethylenically unsaturated monomer (to be describedlater in more detail) which will not react with the isocyanate andhydroxyl groups may be present in the reaction system. The organicsolvent preferabl has a low boiling point since it must be removed afterthe completion of reaction. Examples of such organic solvent are methylethyl ketone, ethyl acetate, propyl acetate, tetrahydrofuran, dioxane,diisopropyl ether, methyl isobutyl ketone, benzene or toluene. Theorganic solvents may be used either alone or in combination.

The reaction temperature may be higher than room temperature, and issuch that the polymerization reaction based on the unsaturated doublebonds present in the reaction system will not be promoted. Unnecessarilyhigh temperatures should be avoided becausesuch high temperaturesinvolve the gelation of the reaction product. In general, the reactiontemperature is from 40 to 120 C., preferably from 50 to 90 C.

For accelerating the rate of reaction, a catalyst such as a quaternaryammonium salt or an organotin compound may be present in the reactionsystem. A polymerization inhibitor may also be added in order to inhibitthe polymerization of the ethylenically unsaturated double bondscontained in the reaction system during the production of theprepolymer. Examples of such polymerization inhibitor includebenzoquinone, 2,5-diphenyl-pbenzoquinone, hydroquinone, hydroquinonemonomethyl ether, catechol or p-ter-butyl catechol. The amount ofpolymerization inhibitor is 0.005 to 1.000% by weight based on the totalweight of the ethylenically unsaturated monomer added to the reactionsystem as required and the prepolymer to be produced.

Examples of the photosensitizer that is incorporated with the prepolymerto form the photosensitive composition of the invention includediketones such as benzil and diacetyl; benzoin and derivatives thereofsuch as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoinbutylether and 'alpha-methylbenzoin; organic sulfides such as diphenylmonosulfide, diphenyl disulfide, desyl phenyl sulfide, andtetramethylthiuram monosulfide; S-acyldithiocarbamates such asS-benzoyl-N,N-dimethyldithiocarbamate andS-(p-chlorobenzoyl)-N,N-dimethyl dithiocarbamate; phenones such asacetophenone, benzophenone, p-bromobenzophenone and4,4-bis(dimethylamino)benzophenone; and organic sulfonyl chlorides suchas benzenesulfonyl chloride, o-toluenesulfonyl chloride and2-naphthalenesulfonyl chloride. Colors such as eosine and thionine mayalso be used. The amount of photosensitizer is from 0.001 to based onthe total weight of the photosensitive composition.

Examples of the ethylenically unsaturated monomer that is incorporatedin the prepolymer and photosensitizer when it is necessary for impartingbetter workability to the photosensitive composition or improving thephysical properties of the flexographic plate, include styrene,chlorostyrene, alpha-methyl styrene, divinyl benzene, methylmethacrylate, n-butyl methacrylate, n-butyl acrylate, n-propyl acrylate,n-propylmethacrylate, isopropyl methacrylate, isopropyl acrylate,n-hexyl acrylate, Z-ethylhexyl acrylate, Z-ethylhexyl methacrylate, amylacrylate, acrylonitrile, ethylene glycol dimethacrylate, ethylene glycoldiacrylate, triethylene glycol dimethacrylate, triethylene glycoldiacrylate, diallylphthalate, diallyl isophthalate, vinyl acetate orvinyl butyrate,-which are not reactive with the isocyanate groups.

As previously stated, such ethylenically unsaturated monomer may beadded to the reaction system in order to perform the reaction smoothly.In this case, the monomer need not to be separated from the prepolymerafter the completion of reaction, unlike the organic solvent,

and therefore, it is more convenient. Furthermore, as the ethylenicallyunsaturated monomer, those ethylenically unsaturated monomers which doreact with the isocyanate groups, such as acrylic acid, methacrylicacid, acrylamide, methacrylamide or the hydroxyl compound A or C may beused. In this case, the monomer is added after the production of theprepolymer, or together with the hydroxyl component in the final step ofproducing the prepolymer.

'The hardness of the fiexographic printing plate produced byphotopolymerizing the photosensitive compo-sition of the presentinvention has close relation with the type and amount of theethylenically unsaturated monomer. Generally, the ratio of theprepolymer to the ethylenically unsaturated monomer is from :0 to 40:60,preferably from 100:0 to 60:40.

When actinic rays having a wavelength of 1800 to 7000 A. are irradiatedon the photosensitive composition so obtained, the composition readilypolymerizes to a rubbery elastomer having excellent resistance to'waterand chemicals. The light source. to be used at this time may be anywhich can generate actinic rays having a wavelength of 1800 to 7000 A.For example, an ultravioletfluorescent lamp, low pressure mercury lamps,high pressure mercury lamps, ultrahigh pressure mercury lamps or carbonarc lamps may be cited.

Flexographic printing plates can be produced from the photosensitivecomposition of the present invention with a very simple operation. Oneexample of the production will be shown below.

A photosensitive element is first prepared by superposing a supportsheet (ii), a layer of the photosensitive composition (iii), atransparent film (iv), a negative or positive film (v) and a glass plate(vi) on a glass plate (1) in this order. The glass plates (i) and (vi)may preferably'be of polished glass sheet of soda glass, Pyrex glass orquartz glass having a thickness of about 0.5 to

to 10 mm. When a part of the photosensitive composition layer (iii) isphotopolymerized, the photocured composition serves as the support sheet(ii), and therefore the support sheet (ii) is not always necessary. Thesupport sheet (ii) may be used in view of economy and the ease ofmounting the fiexographic plate onto the printing cylinder. The supportsheet (ii) may, for example, be a,

rubber sheet, plastic film, metal plate, or woven cloth, etc. Thethickness of the photosensitive composition layer (iii) may be 0.1 to 10mm. The transparent film (iv) is not always necessary, but may be usedfor rendering the separation of the negative or positive film (v) fromthe photosensitive composition layer (iii) easy, and preventing anyinjury to the negative or positive film (v). Suitable examples of suchfilm include cellophane, polyester films, polyethylene films,polypropylene films or polyvinyl chloride films. Thereafter, actinicrays are irradiated from above through the glass plate (vi), and thenegative or positive film (v). Then the exposed portion of thephotosensitive composition layer (iii) is photopolymerized to form arubbery elastomer insoluble in water or an aqueous solution containingan acid, alkali or organic solvent, which forms an image area. Where thesupport sheet (ii) is not used, actinic light is irradiated from belowalso, so that the lower layer of the layer (iii) is photopolymerized toa rubbery elastomer which can be a substitute for the support sheet(ii). The unexposed portion is then removed by dissolving it in water oran aqueous solution containing an acid, alkali or organic solvent,thereby forming a non-image area. Thus, the intended flexographicprinting plate is produced. 4

In order to increase the strength of the fiexographic printing plate, itis finally re-exposed to actinic light. Since the flexographic plate canbe fully photopolymerized even in the presence of oxygen, thisre-exposing operation can printing ink is better than in the case ofusing rubber be performed with a simple operation in air. Of course,printing plates, and the flexographic plate had excellent this operationcan be performed in a stream of an inert printability.

ga sriuchflas nitroghe n gas 1 t d d f th TABLE I e exograp 1c printmgpa e pro uce rom e photosensitive composition of the present inventionhas 5 23%? gf gg gggz g g gg g gi good printabillty, resistance towater, acid, and organic M h l h 1 3 solvents, and has especially goodalkali resistance as comjg g; fig figg fi z: 3 pared with theconventional fiexographic'printing plates 3 Ethyl methacrylate 75 ofsynthetic resin. The photosensitive composition of the 10 invention alsofinds applications as materials for producing various photo-markedsubstances such as name plates, scribed panels and the like.

The following examples will further illustrate the present invention.

EXAMPLES 4 TO 9 Each of the ethylenically unsaturated monomers indicatedin Table II was added to each of the prepolymers prepared from thematerials indicated in Table II to form a 15 prepolymer solution. To thesolution 1% by weight, based EXAMPLES 1 To 3 on the total weight, ofbenzoin methyl ether was added.

Tolylene diisocyanate (2,4-tolylene diisocyanate/2,6- The materials wereuniformly mixed with one another to tolylene-diisocyanate:80/20) 348grams (2.0 moles) was form a photosensitive composition.

heated to 70 C. With care taken not to raise this tem- Using such of thephotosensitive compositions, a fiexoperature, 1000 g. of polyethyleneglycol having an aver- 2 graphic printing plate was produced in the samemanner age molecular weight of 1000 heated at 70 C. were as set forth inExamples 1 to 3. The fiexographic plate added dropwise in the course ofone hour, and the reobtained had good rubbery elasticity and a Shorehardness action was performed for hours. Thereafter, a solution (A)indicated in Table II.

TABLE II Polyiso- Hydroxyl compounds used (g.) cyanate Shore compoundEthylenlcally unsatuhardness B G D (g-) rated monomer (g.) (A) PEG 2000(2,000) 2 HEMA (286) TDI (348) 60 PEG 2000 (2,000) 2 HEMA (286) TDI(348) MMA (292) 79 PEG 2000 (2,000) 2 HEA (255) TDI (348) EA (325 48 PEG1540 (1,230) 2 HEA (255) .8) TDI (376) EA (210)) 65 Polyglycol15-200(2,600) 2 HEMA (429) TDI (522) EA (400) 68 or PE400 (1,030)--. TDI (174)BMA (130) 77 10 Blenmer PE-400 (400)----- PEG 1540 (770) CHPMA (98) TMP(67) TDI (348) EA1(526), TMPTMA 90 11 Blenmer PIE-400 (440)-..-- PEG1540 (770) TDI (174) EA (325), AA (11) 62 The following abbreviationshave been used in Table II.

PE G 1540=po1yethylene glycol with an average molecular weight of 1,540;PE G 2000=polyethylene glycol with an average molecular weight of 2,000;Polyglycol15200==polyether polyol with an average molecular weight of2,600 (product of Dow Chemical Corporation); Blenmer PE 400=p0lyethyleneglycol mouomethacrylate with an average molecular weight of 400 (productof Nippon Oil and Fats 00., Ltd); 2 HEMA=2-hydroxyethyl methacrylate; 2HEA=2-hydroxyethyl acrylate; DP G=dipropylene glycol; TDI=tolylenediisocyanate (isomer ratio 2,4-/2,6 =/20); XDI=xylylene diisocyanate(isomer ratio m-/ 70-75/3025) NMA =methyl methacrylate; EA=ethylacrylate; BMA =n-butyl-methacrylate; CHPMA =3-chloro-2-hydroxypropy1methacrylate; AA =acrylic acid; TM]? TMA =trimethylolpropanetrimethaerylate; TMP =trimethylolpropane.

of 286 g. (2.2 moles) of Z-hydroxyethyl methacrylate and EXAMPLE 120.286 g. of p-benzoquinone were added dropwise over a period of 0.5hour. The reaction was performed for additional 7 hours to form a lightyellow transparent prepolymer.

A photosensitive composition was prepared in the same way as set forthin Example 1 except that 10 g. of a mixture of trimethylol propanetrimethacrylate and tri- To the resulting prepolymer 10 g of each of theethYL ethylene glycol diacrylate (Weight ratio of 7:3) were usedenically unsaturated monomers indicated in Table I and i then-uithyllmethacrylate' d b 1 g. of benzoin methyl ether were added.These were unip otosensltlve e ement was Produce y Suparposmg forr rtrlymixed to form three kinds of photosensitivecomg i' i fif f i 'gz fi15325 2122231? 2 122 posr 101'1S.

A photosensitive element was prepared by superposif g 3 g :g3Z g 21 t? 2i gg 33 2 3 a 3.0 mm. thick layer of photosensitive composinon (n1), g p

4 lass plate (i) in this order. an l8-m1cron thick 01 ester film 1v a neative film g (v), and a 50 mm g z Polished g l plategwi) on a Actmicrays were irradiated onto the glass plate (v1) for 5.0 mm. thickpolished glass plate (i) in this order.

laced at a distance 35 cm. awa The exposed ortion Actimc rays wereirradiated onto the glass plates (1) P y developed with water at 25 C. Aflexo ra hic nutand (v1) from a high pressure mercury lamp (800 w.) at Wg p a distance 35 cm. from the glass plate. The exposure time mg llflateg Lg i q rubbery elastlclty on i 6 glass plate (vi) and 3 minutes forthe l h e i lief iin a ge v v a r eliigb sed in air to actinic rays gass p ate 1 After exposure, the photosensitive composition layer@igfiiifiififi (A) of 89 after re'exposure' (iii) was developed withwater at 25 C. to form a rub- I bery elastomer having a vivid reliefimage, namely, flexo- 5 g g z g gg g z z ig i'g graphic printing plate.I b p p y p 00.5mm Sal Prepo For strengthening the ilexographic plate,it was irramet emg prepare y e reaction of a hydroxy ponent (I) selectedfrom (i) a hydroxy Compound A having at least '5 ether linkages and anethylenically unsaturated double bond expressed by the formula diatedwith actinic rays for 5 minutes in the air from a high pressure mercurylamp placed at a distance 35 cm. away to give each of the flexographicplates a Shore hardness (A) as shown in Table 1.

Using each of the resulting flexographic printing plates, printing wasperformed from an aqueous fiexographic ink R or oleophilic flexographicink on acorrugated board, kraft wherein R is a hydrogen atom or a methylor ethyl paper, cellophane, and polyethylene film. The transfer ofgroup,

5 minutes from a high pressure mercury lamp (800 W.)

(ii). a combination of said hydroxy Compound A and a hydroxy Compound Bhaving at least ether linkages,

(iii) a combination of said hydroxyl Compound A and a hydroxyl CompoundC having an ethylenically un saturated double bond expressed by theformula CH =('JCOO- v wherein R is a hydrogen atom or a methyl'or ethylgroup,

(iv) a combination C, and (v) a combination of said hydroxyl CompoundsA, B

and C with a polyisocyanate component (II).

2. A photosensitive composition comprising a polyurethane prepolymer, aphotosensitizer and an ethylenically unsaturated monomer, saidprepolymer being prepared by the reaction of a hydroxyl component ('I)selected from (i) a hydroxy Compound A having at least 5 ether linkagesand an ethylenically unsaturated double bond expressed by the formula ofsaid hydroxy Compound s B and wherein R is a hydrogen atom or a methylor ethyl p (ii) a combination of said hydroxyl Compound A and a hydroxylCompound B having at least 5 ether linkages, (iii) a combination of saidhydroxyl Compound A and a hydroxy Compound C having an ethylenicallyunsaturated double bond expressed by the formula (wherein n is aninteger of 6 to 200) (b) polyethylene glycol monomethacrylates formulaof the CH1=C-C O O(CH1CH:O)HH

(wherein n is an integer of 6 to 200), (c) polypropylene glycolmonoacrylates of the formula CH:=CHCOO(CH:CHO)H (wherein n is an integerof 6 to 200), (d) polyethylene glycol monoacrylates of the formula(wherein n is an' integer of 6 to 200), an Y (e) hydroxyl compounds ofthe formula onlo CHZCHO H 43H: )1:

GHICHl-CCH1O 01110110 11 H! )Il 01110 CHQCHO OCC=CH1 Ht )1 H" 12(wherein l, m and n are each zero or a positive integer, and satisfy therelation of l+m+n is an integer of S to 200). p 4. The photosensitivecomposition of claim 2, wherein said hydroxyl Compound A is selectedfrom the group consisting of (a) polypropylene glycol monomethacrylatesof the;

formula CHa=(3COO(CH:|CHO)uH CH; CH:

(wherein n is an integer of 6 to 200),

(b) polyethylene glycol monomethacrylates of the formula CH: I

(wherein n is an integer of 6 to 200),

(c) polypropylene glycol monoacrylates of the formula" (wherein n is aninteger of 6 to 200), (d) polyethylene glycol monoacrylates of theformula CH =CHCOO (CH CH O) I-I (wherein n is an integer of 6 to 200),and v (e) hydroxyl compounds of the formula CHzO CHQCHO H L a, CHaCHn--CH2O CHZOHO H a.

CHJO CHzCHQ OCC=CH3 H: )1 CH:

(wherein l, m and n are each zero or a positive integer,

and satisfy the relation of l+m;+n is an integer of 5 to 200).

5. The photosensitive composition of claim 1, wherein said hydroxylCompound C is selected from the group consisting. of 2-hydroxyethy1acrylate, Z-hydroxyethyl methacrylate, 2-hydroxypropy1 acrylate,2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, diethyleneglycol monomethacrylate, glycerol dimethacrylate, an equimolar reactionproduct of glycidyl methacrylate and acrylic acid, trimethylol propanedimethacrylate, trimethylpropane monomethacrylate, pentaerythritoltrimethacrylate, pentaerythritol and pentaerythritol monomethacrylate.

6. The photosensitive composition of claim 2, wherein said hydroxylCompound C is selected from the group consisting of 2-hydroxyethylacrylate, Z-hydroxyethyl methacrylate, Z-hydroxypropyl acrylate,2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, diethyleneglycol monomethacrylate, glycerol dirnethacrylate, an equimolar reactionproduct of glycidyl methacrylate and acrylic acid, trimethylol propanedimethacrylate, trimethylpropane monomethacrylate, pentaerythritoltrimethacrylate, pentaerythritol dimethacrylate and pentaerythritolmonomethacrylate.

7. The photosensitive composition of claim 1, wherein said hydroxylCompound B is selected from the group consisting of (a) polyethyleneglycols of the formula (wherein n is an integer of 6 to 200),

(b) polypropylene glycols of the formula (wherein n is an integer of 6to 200),

(c) polytetramethylene glycols of the formula HO(CH CH CH O),,H

(wherein n is an integer of 6 to 200), (d) polyoxyethylated glycerols ofthe formula CH1O(CHCHQO)|H CH10(CH2CH10) H CHZO (crnomomi (wherein l, mand n are each zero or a positive mteger, and satisfy the relation ofl+m+n is an integer of 5 to 200),

I (e) polyoxypropylated glycerol of the formula CH70(CH:CHO) [H HOCHzCHaO H C lHa )m CH: CH2 C H O H (llHa I:

(wherein l, m and n are as defined above), (f) polyoxyethylatedtrimethylolpropanes of the formula (wherein l, m and n are as definedabove), (g) polyoxypropylated trimethylolpropanes of the formula CHzOCHaC HO H CH3CH2C ---CH: O CH: C H O II-Ia CH2 0 CHQC HO H (wherein l, mand n are as defined above), (h) hydroxyl compounds of the formula(wherein l, m and n are each a positive integer of at least 1 andsatisfy the relation of l+m+n is integer of 5 to 200),

and

(i) poly(3,3-bischloromethyloxyacrylobutane) of the formula CHnClHo(cHiooHi0 H (wherein n is an integer of 6 to 200).

8. The photosensitive composition of claim 2, wherein said hydroxylCompound B is selected from the group consisting of (a) polyethyleneglycols of the formula (wherein n is an integer of 6 to 200), (b)polypropylene glycols of the formula HO CHzCHO H ()H: )1: (wherein n isan integer of 6 to 200), (c) polytetramethylene glycols of the formulaHO (CH CH CH CH O H (wherein n is an integer of 6 to 200),

14 (d) polyoxyethylated glycerols of the formula CH20(CH2CH20)1H CHzO(CH2CH20)mH 2 (CHzCHzOImH (wherein l, m and n are as defined above), (f)polyoxyethylated trimethylolpropanes of the formula (wherein l, m and nare as defined above), (g) polyoxypropylated trimethylolpropanes of theformula H3 in omo CHzGHO H (wherein l, m and n are as defined above),

(h) hydroxyl compounds of the formula (wherein l, m and n are each apositive integer of at least 1 and satisfy the relation of l+m'+n is aninteger of 5 to 200),

and

(i) poly(3,3-bischloromethyloxyacrylobutane) of the formula CHaCl HO(CHZCCHIO) H HzCl 11 (wherein n is an integer of 6 to 200).

References Cited UNITED STATES PATENTS 3,645,730 2/1972 Frank et a1.9635.1 2,948,611 8/1960 Barney 9635.1 3,556,791 1/1971 Suzuki et al9635.1 3,644,120 2/1972 Kai et a1. 96-115 3,658,531 4/1972 Kurtz 9635.l

RONALD H. SMITH, Primary Examiner US. Cl. X.R.

9635.1, P; 204l59.l4, 159.15, 159.16

UNITED STA'I ES IA'lENT OFFICE CERTIFlCATE+01 CORRECTION Patent: No.3,782,961 Dated January 1, 1974- Inventor(s) Katsut'oshi TAKAHASHI E1"AL It: is'certifhied that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

' CH20(CH2CH20) 1H CH3CH2 -C-CH2Q(CH2CH20) H cn own cu m n Column 13,claim 7: cancel the formula (g) thereof and substitute the followingformula therefor:

' I cn 'omn cnm u CIH3 K CH CH Q-CH 0(CH CHO) H V 3 v CHZMCH C OMH 1 3Column 13, claim 7: cancel the formula (h) thereof and substi tute thefollowing formula therefor:

Sheet 4 of 6 FORM P()-1050(10-G9) USCOMM-DC 693764 59 9 US GOVIIRNNFNIPRINTING OFHCII: Hi) D-3fi$-l14 UNITED STATES PATENT OFFICECER'IIFICA'IE 0F CORRECTION Patent No. 3,782 ,961 D ted January 1, 1974Inventor(s) Katsutoshi TAKAHASHI ET AL I It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as'shown below:

Column 13, Claim 7: cancel the formula (i) thereof and substitute thefollowing formula therefor:

CHZCI nomn cl'zcn m n CHZCI' Column 13, Claim 8: cancel the formula (b)'thereof and substitute the following formula thereforzq Ho(cH cH0) HColumn 14, Claim 8: cancel the formula (e) thereof and substitute thefollowing formula therefor:

ca owa cum n Y CH O(CH CHO) H Sheet 5 of 6 m. PO-105O (10459) r UNITEDSTATES PATENT OFFICE- CERTIFICATE QF CORRECTION Sheet 6 of 6 Patent No.3 782 ,961 Dated January 1, 1974' Inventor(s) .Katsntoshi TAKAHASHI E'lAL It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

- Column 14, Claim 8: cancel the formula (g) thereof and substitute thefollowing formula therefor:

h CH MCHZCHO) H CH3 3H 021 -41431 0(cn cnon n CH3 cu own cfum kl Column14, Claim 8: cancel the formula (i) thereof and substitute the followingformula therefor;

"CH Gl HO(CH CI2CH 0) H CHzCl Signed and sealed this 16th day of July1971*.

(SEAL) Attest: I I

MCCOY M. GIBSON, JR. c. MllRSIjALL DANN- Attesting Officer Commlsslonerof Patents USCOMM-DC 603764 69 0 u.s. covinuuzm rglmlmz orrlcgz 95s0-365-134 Foam Po-1o50 (10-69)

